ObjExporter

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Author: KeliHlodversson

Contents

  • 1 Description
  • 2 Usage
  • 3 ObjExporter.cs
  • 4 EditorObjExporter.cs

Description

This is a simple utility class for generating basic obj files from a mesh object. The obj file format was gleaned from various sites found through google like this one

Usage

Either call ObjExporter.MeshToString() to generate a text string containing the obj file or ObjExporter.MeshToFile() to save it directly to a file.

ObjExporter.cs 

using UnityEngine;
using System.Collections;
using System.IO;
using System.Text;
 
public class ObjExporter {
 
    public static string MeshToString(MeshFilter mf) {
        Mesh m = mf.mesh;
        Material[] mats = mf.renderer.sharedMaterials;
 
        StringBuilder sb = new StringBuilder();
 
        sb.Append("g ").Append(mf.name).Append("\n");
        foreach(Vector3 v in m.vertices) {
            sb.Append(string.Format("v {0} {1} {2}\n",v.x,v.y,v.z));
        }
        sb.Append("\n");
        foreach(Vector3 v in m.normals) {
            sb.Append(string.Format("vn {0} {1} {2}\n",v.x,v.y,v.z));
        }
        sb.Append("\n");
        foreach(Vector3 v in m.uv) {
            sb.Append(string.Format("vt {0} {1}\n",v.x,v.y));
        }
        for (int material=0; material < m.subMeshCount; material ++) {
            sb.Append("\n");
            sb.Append("usemtl ").Append(mats[material].name).Append("\n");
            sb.Append("usemap ").Append(mats[material].name).Append("\n");
 
            int[] triangles = m.GetTriangles(material);
            for (int i=0;i<triangles.Length;i+=3) {
                sb.Append(string.Format("f {0}/{0}/{0} {1}/{1}/{1} {2}/{2}/{2}\n", 
                    triangles[i]+1, triangles[i+1]+1, triangles[i+2]+1));
            }
        }
        return sb.ToString();
    }
 
    public static void MeshToFile(MeshFilter mf, string filename) {
        using (StreamWriter sw = new StreamWriter(filename)) 
        {
            sw.Write(MeshToString(mf));
        }
    }
}


EditorObjExporter.cs 

/*
Based on ObjExporter.cs, this "wrapper" lets you export to .OBJ directly from the editor menu.
 
This should be put in your "Editor"-folder. Use by selecting the objects you want to export, and select
the appropriate menu item from "Custom->Export". Exported models are put in a folder called
"ExportedObj" in the root of your Unity-project. Textures should also be copied and placed in the
same folder.
N.B. there may be a bug so if the custom option doesn't come up refer to this thread answers.unity3d.com/questions/317951/how-to-use-editorobjexporter-obj-saving-script-fro.html */
 
using UnityEngine;
using UnityEditor;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Text;
using System;
 
struct ObjMaterial
{
	public string name;
	public string textureName;
}
 
public class EditorObjExporter : ScriptableObject
{
	private static int vertexOffset = 0;
	private static int normalOffset = 0;
	private static int uvOffset = 0;
 
 
	//User should probably be able to change this. It is currently left as an excercise for
	//the reader.
	private static string targetFolder = "ExportedObj";
 
 
    private static string MeshToString(MeshFilter mf, Dictionary<string, ObjMaterial> materialList) 
    {
        Mesh m = mf.sharedMesh;
        Material[] mats = mf.renderer.sharedMaterials;
 
        StringBuilder sb = new StringBuilder();
 
        sb.Append("g ").Append(mf.name).Append("\n");
        foreach(Vector3 lv in m.vertices) 
        {
        	Vector3 wv = mf.transform.TransformPoint(lv);
 
        	//This is sort of ugly - inverting x-component since we're in
        	//a different coordinate system than "everyone" is "used to".
            sb.Append(string.Format("v {0} {1} {2}\n",-wv.x,wv.y,wv.z));
        }
        sb.Append("\n");
 
        foreach(Vector3 lv in m.normals) 
        {
        	Vector3 wv = mf.transform.TransformDirection(lv);
 
            sb.Append(string.Format("vn {0} {1} {2}\n",-wv.x,wv.y,wv.z));
        }
        sb.Append("\n");
 
        foreach(Vector3 v in m.uv) 
        {
            sb.Append(string.Format("vt {0} {1}\n",v.x,v.y));
        }
 
        for (int material=0; material < m.subMeshCount; material ++) {
            sb.Append("\n");
            sb.Append("usemtl ").Append(mats[material].name).Append("\n");
            sb.Append("usemap ").Append(mats[material].name).Append("\n");
 
            //See if this material is already in the materiallist.
            try
       		{
          		ObjMaterial objMaterial = new ObjMaterial();
 
          		objMaterial.name = mats[material].name;
 
          		if (mats[material].mainTexture)
          			objMaterial.textureName = EditorUtility.GetAssetPath(mats[material].mainTexture);
          		else 
          			objMaterial.textureName = null;
 
          		materialList.Add(objMaterial.name, objMaterial);
        	}
        	catch (ArgumentException)
        	{
            	//Already in the dictionary
        	}
 
 
            int[] triangles = m.GetTriangles(material);
            for (int i=0;i<triangles.Length;i+=3) 
            {
            	//Because we inverted the x-component, we also needed to alter the triangle winding.
                sb.Append(string.Format("f {1}/{1}/{1} {0}/{0}/{0} {2}/{2}/{2}\n", 
                    triangles[i]+1 + vertexOffset, triangles[i+1]+1 + normalOffset, triangles[i+2]+1 + uvOffset));
            }
        }
 
        vertexOffset += m.vertices.Length;
        normalOffset += m.normals.Length;
        uvOffset += m.uv.Length;
 
        return sb.ToString();
    }
 
    private static void Clear()
    {
    	vertexOffset = 0;
    	normalOffset = 0;
    	uvOffset = 0;
    }
 
   	private static Dictionary<string, ObjMaterial> PrepareFileWrite()
   	{
   		Clear();
 
    	return new Dictionary<string, ObjMaterial>();
   	}
 
   	private static void MaterialsToFile(Dictionary<string, ObjMaterial> materialList, string folder, string filename)
   	{
   		using (StreamWriter sw = new StreamWriter(folder + "/" + filename + ".mtl")) 
        {
        	foreach( KeyValuePair<string, ObjMaterial> kvp in materialList )
        	{
        		sw.Write("\n");
        		sw.Write("newmtl {0}\n", kvp.Key);
        		sw.Write("Ka  0.6 0.6 0.6\n");
				sw.Write("Kd  0.6 0.6 0.6\n");
				sw.Write("Ks  0.9 0.9 0.9\n");
				sw.Write("d  1.0\n");
				sw.Write("Ns  0.0\n");
				sw.Write("illum 2\n");
 
				if (kvp.Value.textureName != null)
				{
					string destinationFile = kvp.Value.textureName;
 
 
					int stripIndex = destinationFile.LastIndexOf('/');//FIXME: Should be Path.PathSeparator;
 
       				if (stripIndex >= 0)
            			destinationFile = destinationFile.Substring(stripIndex + 1).Trim();
 
 
            		string relativeFile = destinationFile;
 
            		destinationFile = folder + "/" + destinationFile;
 
					Debug.Log("Copying texture from " + kvp.Value.textureName + " to " + destinationFile);
 
					try
					{
						//Copy the source file
						File.Copy(kvp.Value.textureName, destinationFile);
					}
					catch
					{
 
					}	
 
 
					sw.Write("map_Kd {0}", relativeFile);
				}
 
				sw.Write("\n\n\n");
        	}
        }
   	}
 
    private static void MeshToFile(MeshFilter mf, string folder, string filename) 
    {
    	Dictionary<string, ObjMaterial> materialList = PrepareFileWrite();
 
        using (StreamWriter sw = new StreamWriter(folder +"/" + filename + ".obj")) 
        {
        	sw.Write("mtllib ./" + filename + ".mtl\n");
 
            sw.Write(MeshToString(mf, materialList));
        }
 
        MaterialsToFile(materialList, folder, filename);
    }
 
    private static void MeshesToFile(MeshFilter[] mf, string folder, string filename) 
    {
    	Dictionary<string, ObjMaterial> materialList = PrepareFileWrite();
 
        using (StreamWriter sw = new StreamWriter(folder +"/" + filename + ".obj")) 
        {
        	sw.Write("mtllib ./" + filename + ".mtl\n");
 
        	for (int i = 0; i < mf.Length; i++)
        	{
            	sw.Write(MeshToString(mf[i], materialList));
            }
        }
 
        MaterialsToFile(materialList, folder, filename);
    }
 
    private static bool CreateTargetFolder()
    {
    	try
    	{
    		System.IO.Directory.CreateDirectory(targetFolder);
    	}
    	catch
    	{
    		EditorUtility.DisplayDialog("Error!", "Failed to create target folder!", "");
    		return false;
    	}
 
    	return true;
    }
 
    [MenuItem ("Custom/Export/Export all MeshFilters in selection to separate OBJs")]
    static void ExportSelectionToSeparate()
    {
    	if (!CreateTargetFolder())
    		return;
 
        Transform[] selection = Selection.GetTransforms(SelectionMode.Editable | SelectionMode.ExcludePrefab);
 
        if (selection.Length == 0)
        {
        	EditorUtility.DisplayDialog("No source object selected!", "Please select one or more target objects", "");
        	return;
        }
 
        int exportedObjects = 0;
 
       	for (int i = 0; i < selection.Length; i++)
       	{
       		Component[] meshfilter = selection[i].GetComponentsInChildren(typeof(MeshFilter));
 
       		for (int m = 0; m < meshfilter.Length; m++)
       		{
       			exportedObjects++;
       			MeshToFile((MeshFilter)meshfilter[m], targetFolder, selection[i
		

		

		    

		        
		    

		


		

	        
		

		    

		        
		        

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